The present invention relates to a motor vehicle headlight having a device for measuring the amount of deviation of the light beam from the headlight in vertical and horizontal directions from a proper aiming direction.
A headlight is generally provided with an aiming mechanism for rotatably adjusting the headlight about prescribed horizontal and vertical axes to adjust the direction of the optical axis of the headlight in such a manner as to align the light beam therefrom in a prescribed range. For this adjustment, the headlight is lit in a dark room, and the light beam from the headlight is shone onto a screen placed at a prescribed distance therefrom. The headlight is then adjusted until the beam on the screen is at a prescribed position.
For this adjustment, much equipment, such as a large dark room and screen, is required. Moreover, it is time consuming to perform the adjustment because it is necessary to align the spot of the light beam while looking at the screen.
Headlights used in the United States have three location bosses, which define measurement reference surfaces, projecting from the front lens of the headlight. To perform headlight alignment, a measuring instrument called an "aimer" is set in contact with the location bosses to first determine whether or not the headlight is inclined relative to a horizontal plane. The headlight is attached to the motor vehicle in such a manner that the front surfaces of the location bosses, which are the measurement reference surfaces, extend vertically when the vehicle is on a horizontal surface . When the measuring instrument is set in contact with the vertically extending front surfaces of the location bosses, the amount of inclination of the headlight relative to the horizontal plane is measured. It is required that the measured value be within a prescribed range.
To be able to carry out such measurements, every headlight used in the United States must have the above-described location bosses. However, different alignment techniques are used in most other countries. For that reason, headlights for U.S. use must be manufactured separately and differently from those to be used in Japan, Europe, etc. This is troublesome and expensive.